Arrangements for acquiring and using data obtained from received interference to facilitate data recovery

ABSTRACT

In some embodiments a method is disclosed for detecting periodic interference and predicting future interference times. The method can include detecting an arrival time of a first occurrence of interference and detecting an arrival time of a second occurrence of interference. The method can include transmitting preemptive interference mitigation control signals that anticipate future arrival times of interference. A system is disclosed that includes a periodicity detector, an interference profiler and a mitigation control module. The system can provide interference mitigation features to a data recovery system. Other embodiments are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to a provisional application No.60/940,304, entitled Noise Mitigation, filed on May 25, 2007. Thecontents of provisional application No. 60/940,304 are herebyincorporated by reference.

FIELD

The present disclosure is related to the field of wirelesscommunication, and more particularly, to the field of mitigatinginterference in data recovery systems.

BACKGROUND

Wireless communications systems have become ubiquitous. With so manysystems emitting radio frequency energy, the environment is filled withenergy that can interfere with systems that are trying to communicate.Many wireless systems such as wireless local area networks, cordlesstelephones and Bluetooth® compatible devices transmit a low power signalwhere interfering signals often have energy levels that are magnitudesgreater than low power systems. Accordingly, it can be difficult tocommunicate low power digital data with such high levels ofinterference.

Many wireless communication systems utilize a wideband topology.Wideband receivers can simultaneously transmit and receive on numerousfrequencies within a given bandwidth. Many wideband receivers, such asthose utilized by wireless local area networks (WLANs), can be subjectedto narrow band interference from other devices that emit interferencehaving frequencies that fall within the pass band of the widebandreceiver. Some interfering devices may not even be communicationsystems. For example, microwave ovens and motors can emit interference.

To address such interference there has been significant effort in thefield of noise mitigation. One such interference mitigation technique isnoise cancellation, where disruptive noise can be detected and inverted(shifted 180 degrees) to create an anti-phase signal that can be addedto a delayed incoming signal. Such a process can cancel at least aportion of the noise component, making it easier for a system to recoverdata over a wireless link. Traditional systems often have multiplereceive paths, one path for the desired signal and another path forgenerating the anti-phase signal. Thus, wideband receivers that utilizefour channels often have eight receive paths. Other traditionalinterference mitigation systems utilize filtering processes. Thesefiltering processes are generally not effective for mitigatinginterferences that have frequency that fall within the receiver passband because filter these frequencies degrades the desired signal.

Narrowband interference is a type of electromagnetic interference thatoften occurs at relatively high levels in a band of frequencies that aresmaller or narrower than the total bandwidth of the receiverexperiencing interference. One common type of narrow band interferencethat is problematic for WLAN type devices comes from radios transmittingvoice or data at low rates. A few examples of such narrow band typedevices can include cell phones such as global system for mobilecommunications (GSM) phones, Bluetooth® compatible devices and cordlessphones.

Generally, TDMA (time division multiple access) type devices areallocated a time slot in which they can transmit and receive, and thusTDMA devices create periodic interference or high level burstinterference that can be disruptive for systems that operate at lowsignaling levels. Although such devices are typically assigned an“exclusive” frequency band, sidebands or harmonics of the transmittedfrequency that are emitted often fall within the active bandwidth forother systems.

One current standard for the wideband wireless local area networks isthe Institute of Electrical and Electronic Engineers (IEEE) 802.11standard, originally published in October of 1999. The 802.11 standardspecifies that WLAN device enter a power conservation mode (and nottransmit or receive) when the signal being received is less than apredetermined amount over the noise level. This standard caters tobattery powered WLAN compatible devices because if no signal isavailable for reception, the system can enter the sleep mode to conservebattery power. High levels of interference can mask the desired signalso that the WLAN receiver is unable to correctly operate in the powerconservation mode.

While filtering techniques can be used to remove certain types ofinterference, filtering can also cause a loss of data, since filteringtypically degrades the signal or removes part of the desired signal.Some have attempted to utilize a tap notch finite impulse response (FIR)filter to mitigate interference though filtering. This approach is notvery practical because the length of the notch filter (required samplingsize) is typically too large, and such a filter requires more than aWLAN preamble length for initialization. For example, a typically WLANcompatible transmission has a preamble with 10 standard transferspecification (STS) which requires 160 samples. The overall latencycreated by such a FIR filter is too high, and the complexity of such asystem is also a limiting factor.

As stated above, the feature in the IEEE 802.11 specification that isintended to reduce power consumption of a WLAN receiver when a useablesignal is not present often causes a dropped communication. In addition,802.11 compliant systems can easily be jammed with an interfering signaleven though proper interference mitigation would allow an 802.11compliant signal to be effectively processed by the receiver.Traditional receiving systems without robust interference mitigationsystems often have communication failures, even in the middle of packetreception. Thus, most traditional receiving systems have less thanperfect interference mitigation systems, and such systems will drop acommunication session even though with proper mitigation a useablesignal would be present and communications could continue uninterrupted.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the disclosure will become apparent upon reading thefollowing detailed description and upon reference to the accompanyingdrawings in which, like references may indicate similar elements:

FIG. 1 is a block diagram of a data recovery system with an interferencemitigation system;

FIG. 2 is a block diagram of an interference mitigation system with adata recovery system;

FIG. 3 is a block diagram of an interference detection system;

FIG. 4 is a flow diagram depicting a method for detecting and mitigatingnoise in a data recovery system;

FIG. 5 is a flow diagram depicting another method for detecting andmitigating noise in a data recovery system;

FIG. 6 is a flow diagram illustrating yet another method for mitigatinginterference;

FIG. 7 is a flow diagram depicting a method for cancelling interference

FIG. 8 is a flow diagram illustrating another method for cancellinginterference;

FIG. 9 is a graph of a received signal and interference estimation;

FIG. 10 is a graph of a received signal where the interference has beensubtracted from the received signal; and

FIG. 11 is a flow diagram depicting yet another method for cancellinginterference

DETAILED DESCRIPTION OF EMBODIMENTS

The following is a detailed description of embodiments of the disclosuredepicted in the accompanying drawings. Systems and methods are disclosedwherein a desired signal component of a received signal can be filteredout to create a signal with an emphasized interference component. Anequation can be generated that estimates the resulting interferencewaveform. An anti-phase version of the equation can be created and thenadded to the received signal to reduce the interference portion or toremove at least a portion of the interference component from thereceived signal. Accordingly, a robust data signal representing thedesired component can be extracted from the resulting signal and thissignal can be provided to a data recovery system.

In some embodiments a system is disclosed that can mitigate interferencecaused by devices that are compatible with a global system for mobilecommunications (GSM) system. These GSM compatible transmissions ofteninterfere with WLAN compatible receivers. The embodiments are in suchdetail as to clearly communicate the disclosure. However, the amount ofdetail offered is not intended to limit the anticipated variations ofembodiments. On the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the present disclosure as defined by the appended claims.

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particularstructures, architectures, interfaces, techniques, etc. in order toprovide a thorough understanding of the various aspects of thedisclosure. However, it will be apparent to those skilled in the arthaving the benefit of the present disclosure that the various aspects ofthe disclosure may be practiced in other examples that depart from thesespecific details. In certain instances, descriptions of well-knowndevices, circuits, and methods are omitted so as not to obscure thedescription herein with unnecessary detail.

While specific embodiments will be described below with reference toparticular configurations of hardware and/or software, those of skill inthe art will realize that the disclosed embodiments may advantageouslybe implemented with other equivalent hardware and/or software systems.Aspects of the disclosure described herein may be stored or distributedon computer-readable media, including magnetic and optically readableand removable computer disks, as well as distributed electronically overthe Internet or over other networks, including wireless networks. Datastructures and transmission of data (including wireless transmission)particular to aspects of the disclosure are also encompassed within thescope of the disclosure.

Ideally, a WLAN device with a robust interference mitigation system willsynchronize with a transmitter, commence packet processing and continuepacket processing as long as a signal can be detected, irrespective ofburst or narrowband interference. As discussed in the background,wideband data receivers, such as IEEE 802.11 compatible WLAN receivers,are often subjected to interferences including high level interferenceof a periodic burst or continuous nature.

One specific embodiment disclosed is the mitigation of interference froma third harmonic of a GSM type cell phone that falls into the frequencyband utilized by WLAN receivers. The arrangements described may be usedalone or in combination with other interference mitigation to mitigatehigh levels of narrowband interference that fall within the pass band ofa wideband victim receiver

As stated above a number of wireless devices operate using a timedivision multiple access protocol that, is difficult to accuratelydetect and quantify. It can be appreciated that the arrangementsdisclosed can accurately detect TDMA based interference and such adetection and quantification of this TDMA interference can be utilizedto provide superior cancellation of such time based interference.

Typical wideband receivers are designed with a small dynamic range suchthat they can be economically manufactured. Dynamic range can bedescribed as range of signal levels that the receiver can effectivelyprocess. Alternately described, the dynamic range of a receiver can bedefined by the ratio of the maximum signal level to minimum signal levelthat a system can effectively process. It can be appreciated that as thedynamic range and signal level of a receiver design decreases, itbecomes more difficult to mitigate interference. This occurs becauserelatively high levels of burst interference can saturate the amplifiersof the system. When these amplifiers are saturated, interferencecancellation subsystems cannot effectively operate and hence in suchcircumstances data recovery from the desired signal cannot be accuratelyperformed.

In an 802.11 compatible device, when the signal level of the desiredsignal on one or more channels goes below the noise level or drops morethan 3 dB due to incoming interference, the device will often enter a“sleep mode,” thereby dropping a current communication session. Thisoften occurs even though the interference is temporary and a robust orcomprehensive interference detection/mitigation system could prevent thedropping of communication sessions and can facilitate continued datarecovery during periods of interference. Alternately stated, sporadic orperiodic interference from time domain based devices, even though shortlived, if not mitigated can severely interrupt communications even inthe middle of receiving a packet.

As stated in the background, one significant interferer with 802.11compliant WLAN communications is transmitting GSM compatible devices.Although such devices are assigned a different operating frequency thanan 802.11 compatible device, a GSM system often emits sideband power orharmonic power (typically a third harmonic) having frequencies that fallwithin the frequencies assigned to 802.11 compliant devices. Suchinterference can cause significant interference because GSM devicesutilize relatively high power levels. As stated above, such a GSMtransmission will often disrupt and terminate WLAN communications evenduring the middle of a packet reception.

Many traditional cancellation type interference mitigation systems crossmodulate to cancel the noise portion of the received signal. Crossmodulation is a multiplicative process caused by non linearity. Othersystems utilize a linear summation process in which an inverted replicaof the interference is added to the signal. A phase shifting plusamplitude weighting can be done to ensure that the two replica signalshave an “exact” anti-phase and the amplitude weighting is utilized tomatch the amplitudes of the signals so that complete cancellation canoccur.

As described below, the disclosed system can detect the existence ofdifferent types of interference and profile the detected interference.The disclosed system can utilize a variety of specialized sensors whereeach sensor can detect one or more characteristics of the interference.Each sensor can produce one or more control signal(s) to one or moreinterference mitigation modules. Thus, based on the type of interferencedetected, or the characteristics of the interference detect, multipleinterference mitigation modules or sub-systems can be controlled, suchthat the sub-systems perform in a coordinated manner to providesubstantial mitigation of the detected interference.

It can be appreciated that there are many types of interferences, orthat interferences can have many different characteristics whereinterference with different characteristics (that can be quantified) canbe more effectively mitigated with a tailored or specialized mitigationsystem. There are an infinite number of different interferencecharacteristics that can negatively affect a data recovery system andthese characteristics can even change many times per second. Thus, itcan be appreciated that it is beneficial to provide a system that candetect different types and characteristics of interference and define orprofile the interference that is disrupting data recovery such that aneffective remedy can be implemented in real time.

Based on the profile of the interference a mitigation control system canselect, and control a type of interference mitigation feature in one ormore stages of the data recovery system to provide effective mitigationof the detected interference. Such detection and selection can beperformed in real time and thus, dynamic based interference mitigationcontrol can be achieved. In addition, based on detected interference,multiple receiver control sub systems, that are mutually exclusive, canbe activated concurrently to better facilitate effective interferencemitigation processes within the system. It can be appreciated thatimplementing interference mitigation processes and systems that aretailored to mitigate interference caused by interference energy withparticular detected characteristics can significantly increase theperformance of data recovery systems.

One specialized interference detection system disclosed is a narrow bandinterference detection system for an 802.11 compliant system. In thedisclosed narrowband interference detection system, an incoming widebandsignal can be divided into electromagnetic energy that has specificfrequency ranges or sub bands. The sub bands can have adjacent frequencyranges from a lowest frequency range to a highest frequency range, whereeach sub band can have a contiguous frequency with an adjacent sub band,except for the end bands.

In one embodiment, a narrow band interference profiler for an 802.11compatible system can have a center frequency of 5.8 GHz and a bandwidthof 20 MHz. The 20 MHz bandwidth can be divided into four 5 MHz subbands. Although the disclosed embodiment divides the incoming energyinto four equal sub-bands, this is not a limiting factor. Separating thewideband signal into sub bands allows the energy for each sub band to bedetermined. In some embodiments the energy levels can be compared to athreshold value to determine its relative level.

Many narrow band interfering systems, such as a GSM system, will emitonly a limited number of frequencies in the 20 MHz range. These limitednumbers of frequencies will typically fall into a single sub-band. Wheninterference is detected in a single sub band, or even two of the subbands the narrow band interference profiler can create a narrow bandinterference detection signal and/or a signal that indicates which subbands of frequencies are experiencing interference, and how muchinterference is being received on each sub band.

To determine such parameters, the interference profiler can compare therelative energy levels present in each of the sub bands, and determinewhether the interference present is narrow band interference. Narrowband interference occurs when high interference levels are not detectedin all sub bands. Such a detection of narrow band interference can beutilized to distinguish narrow-band noise from broad-band noise, whichwill typically manifest as relatively high energy levels in all subbands. Alternatively stated, broad-band noise, such as white noise,typically occurs across the entire bandwidth of the receiving system andis prominent when no WLAN compatible transmissions are present.

In some embodiments, in response to the sub band that is experiencinginterference, the narrow band interference profiler can activate aspecific pass band filter, or filter function, that is centered at theinterference frequency(ies). Such a filter can enhance the level of orisolate the interference portion of the received signal or the narrowband interference with respect to the wideband signal. Isolating theinterference portion of the received signal allows for more accurateextraction of the phase and amplitude of the interfering signal. Inaccordance with the present disclosure the isolated/accurately detectedphase and amplitude portion of the interference can be utilized by aninterference cancellation system to generate an anti-phase signal tocancel the interference portion of the received signal

Another specialized interference detection module, such as a timedetection module, can time sample the interference signal to determineif the interference is periodic (i.e. from a time domain system). Thus,an asserted narrow band interference detection control signal incombination with an asserted periodic interference control signal cancreate a profile.

Accordingly, the disclosed system can identify a specific type ofinterference and provide different control signals or output signalsbased on the detection or determination. The disclosed interferenceprofiler can provide a plurality of different control signals that canactivate multiple types of interference mitigation systems and/orprocesses. It can be appreciated that specific types of interferencemitigation systems or interference mitigation methods are more effectivefor specific types of interference. It can also be appreciated that whenthe disclosed arrangements are utilized by 802.11 compliant systemsduring a communication session, the system can detect narrow band timedomain interference and send a control signal to disable a sleep modemodule, such that if the received signal changes by more than apredefined level, typically three dB, the system will not ceasecommunications.

Referring to FIG. 1, an embodiment of a wideband communication system100 that includes a data recovery system (DRS) 101, and an interference(I/F) detection and control (CTL) module 116, is disclosed. In FIG. 1,the data recovery system 101 has more detail and in FIG. 2, the I/Fdetection and control module has more detail. Thus, the systems of FIG.1 and FIG. 2 have like components. The data recovery system 101 caninclude an antenna 102, a down converter 104, a variable gain amplifier(VGA) 106, an automatic gain controller (AGC) 111, an analog to digitalconverter (ADC) 108, a synchronization module 130, a power conservationcontrol (PCC) module 114, a fast Fourier transform module 109 and a datarecovery module 110.

The communication system 100 can also include a parallel to serialconverter 118. The parallel to serial converter 118 can accept aplurality of inputs from data recovery systems, such as data recoverysystem 101, 122, 124, and 126. The communication system 100 can requestand receive data such that the data can be displayed to a user.

In operation, a signal can be received via antenna 102 and theelectromagnetic energy of the received signal can be down converted bydown converter 104 and provided to VGA 106. The down converter can be amixer. The VGA 106 can amplify the signal and the ADC 108 can convertthe received analog signal into a digital signal. The AGC 111 canprovide a gain control signal to the VGA 106, thereby keeping the VGA inan acceptable operating range.

The received signal, a processed received signal and various otheroperating parameters of the data recovery system 101 can be provided tothe I/F detection and control system 116. The I/F detection and controlsystem 116 can detect interference characteristics by directlyprocessing the received signal or processing a version of the receivedsignal that has been processed or can detect abnormal parameters of thedata recovery system 101 and can send a corrective control signal to thedata recovery system 101. It can be appreciated that the I/F detectionand control module 116 is connected to each module (i.e. 104, 106, 108,130, 110, 111 and 114) such that the I/F detection and control module116 can detect interference or its consequences and can activate aninterference mitigation system or process at most locations in the DRS101.

The I/F detection and control module 116 can select an interferencemitigation solution in real time based on detected characteristics ofthe interference and can select and implement a mitigation solution thatis a “best fit.” Such a comprehensive interference detection andcorrection feature can significantly increase the reliability ofcommunications. The latency introduced by the disclosed system issignificantly less than the latency allowed by most currentcommunication standards, such as the IEEE 802.11 standard.

Many systems have a power consumption control system such as PCC 114. Intraditional systems, interference can cause a PCC to place a system in a“low power” or “sleep mode.” In some embodiments, the I/F detection andcontrol module 116 can control the PCC 114 and not allow the PCC 114 toplace the system 101 in a sleep mode due to particular types ofinterference that can cause changes in signal levels. Cell phones oftencreate this type of interference. The disclose interferenceidentification/mitigation system 100 can also be utilized with mosttransmission content types, and can allow a user to simultaneously talkon their cellular based telephone and conduct a voice call, whilereceiving internet content and e-mail or video on their computer.

As stated above, typical wideband data receivers have a very limiteddynamic range, and the amplifiers of such receivers are often subjectedto periodic bursts of interference. Such bursts can force an amplifierto the top of its active range or even the bottom of its active range.When this happens, data cannot be recovered from the received signal.Thus, when a burst of interference enters a VGA, the VGA can becomesaturated or under run, where the VGA does not amplify the desiredsignal and communication failures often result. When specificinterference parameters are detected by the I/F detection and controlmodule 116, the I/F detection and control module can control the AGC 111such that it prevents the VGA 106 from becoming saturated or underrunning due to the interference. Such readjustment of the gain canreduce or eliminate system failures and communication failures.

The interference system 100 can maintain a dynamic operating range for areceiver in the presence of periodic narrowband interference throughoutthe period of the interference and during packet reception. Otherinterference mitigation techniques suffer from transitions in signallevels which often saturate or under drive (i.e. do not provide enoughsignal) the analog to digital converter (ADC). As stated above such acondition often creates unusable data. The FFT module 109 can provide afrequency spectrum estimation of the received signal.

The above discussion has been focused on a single incoming signal. Inthe case of wideband communications such as 802.11 compliantcommunications, many different communication channels can be utilizedconcurrently and these channels comply with orthogonal frequencydivision multiplexing symbols. In embodiments that support 802.11compatible systems, the interference can be estimated and cancelled inthe time domain prior to the FFT 109. Alternatively, provided that thereis sufficient dynamic range, the cancellation could be performed afterthe FFT so that cancellation only occurs in those frequency bins inwhich the interference occurs. It can be appreciated that only onechannel has been discussed above for simplicity but interference formany different channels can also be mitigated concurrently.

Referring to FIG. 2, an embodiment of a wideband communication system200, similar to the embodiment of FIG. 1, is illustrated. In FIG. 1, thedata recovery system 101 has more detail than the data recovery system201 of FIG. 2. In FIG. 2, the I/F detection and control module 216 hasmore detail than the I/F detection and control module 116 of FIG. 1. Thesystem 200 can include a data recovery system 201 that accepts a signalon antenna 202 and provides data at its output 206 and an I/F detectionand control module 216.

The I/F detection and control module 216 can include an interferencesensor/detection subsystem 210, a desired signal filter 221 an I/Festimator 222 that is supported by Vandermonde matrix processor module224, a least square calculation module (LSM) 226 and a recursion module,or recalculation module, (REC MOD) 228. The I/F detection and controlmodule 216 can also include a phase detector (PD) 225, an interferencemitigation control system 232, and an interference profiler 236 with alibrary that can store interference profiles and their associatedmitigation control signals. The associated mitigation control signalscan provide one or more control signals or algorithms that are proven tomitigate interference with a particular profile.

The REC MOD 228 may couple with the I/F estimator 222 to determine anerror in the interference mitigated signal and to recalculate theinterference mitigated signal utilizing the error. The REC MOD 228 mayrecalculate the interference mitigated signal utilizing the error byaltering the polynomial equation utilizing the error. And the REC MOD228 may recalculate the interference mitigated signal utilizing theerror by altering the first set of digitized data based on the error.Further embodiments may involve incrementing a counter based onrecalculating the interference mitigated signal. Further embodiments mayinvolve incrementing a counter based on recalculating the interferencemitigated signal. And still further embodiments may involve storing anumber and if the counter reaches the number, ceasing a recalculationprocess.

In some embodiments, the I/F detection and control module 216 canprovide interference cancellation features. The interferencecancellation features provided by the I/F detection and control module216 can include a data vector module to detect a data vector from areceived transmission, a polynomial generator module to generate apolynomial equation representing interference and a subtraction moduleto subtract the polynomial equation from the received transmission. TheI/F detection and control module 216 can also include a phase inverterto invert the phase of the polynomial equation to facilitate thesubtraction.

The I/F sensor/detection subsystem 210 can include components enclosedby dashed line 210. The I/F sensor/detection and control module 210 caninclude a sample and store module 212, an I/F timing detection module214, an I/F frequency and frequency band detection module 215, an I/Fband width detection module 218, and an I/F magnitude detection module220. The I/F sensor/detector subsystem 210 can detect periodicinterferences emitted from time domain multiple access (TDMA) compatibledevices, high clocks and from signals with periodic frequency andhopping sequences, such as Bluetooth® compatible systems, to name a few.

The components of I/F sensor/detection sub system 210 can bespecialized. The I/F sensor/detection sub system 210 can detect multipleinterference parameters, interference characteristics and abnormaloperating conditions of the DRS 201. For example, the sample and storemodule can sample and store data relating to the input signal and canalso accept monitor outputs of the DRS 201. Some interference maymanifest as abnormal conditions at various locations with the DRS 201,and the sample and store module 212 can detect abnormalities caused bysuch interference and store data related to such abnormalities.

The I/F timing detection module 214 can detect and convey nearly alltiming parameters related to an interfering signal. The I/F timingdetection module 214 can be a time domain interference detector. The I/Ftiming detection module 214 can have a timer or a time clock to timestamp data that defines timing attributes of the interference. Forexample, the I/F timing detection module 214 can detect and provide realtime data or relational timing data regarding a start time, an end time,a duration of pulsed interference and can provide synchronizationinformation that can be utilized to predict a time when the nextinterference pulse can be expected.

The I/F profiler 236 can compare this timing information with a timingsignature for known communication standards from the library to identifyan interference and predict future interferences and control the DRS 201accordingly. The library can store digital data templates representingknown timing patterns for standardized communication protocols. The I/Ffrequency/frequency band detection module 215 can detect the frequencyor frequencies of the interfering signal and/or can detect a band offrequencies that are creating interference. The I/F bandwidth detector218 can detect the bandwidth of the interference.

The I/F bandwidth detector 218 can make a relative determination, ofwhether the received interference is narrow band or broad band. In someembodiments, the I/F bandwidth detector 218 can distinguish whether theinterference is at the noise floor or is “white noise.” As stated above,a received signal has an interference component and a desired signalcomponent. The I/F detection and control module 216 can facilitateseparating the desired signal from the interference component such thatdata can be recovered from the received signal. In some embodiments, thedesired signal filter 221 can be tuned to filter the desired signal outof the received signal to sharpen the characteristics of theinterference component.

The filter 221 can reduce the magnitude of the desired signal inrelation to the interference component. The filtered signal can beprovided to the I/F estimator 222. The filtered signal can allow the I/Festimator 222 to provide a more accurate estimation of the interferencecomponent of the received signal. Although not illustrated, allcomponents of the I/F sensor/detection sub system 210 could be providedwith the filtered signal from the desired signal filter 221.

The I/F magnitude detector 220 can detect the energy level of differentfrequencies or bandwidths of the interfering signal. Generally, the I/Fsensor/detection sub system 210 can detect different characteristics ofharmful interference and can provide detailed information about suchinterference, including the attributes of interference, theclassifications or profiles of the interference, the frequency(ies) andbandwidth, the magnitudes, and the timing arrangements and abnormalconditions in the DRS 201.

In operation, the I/F mitigation control module 232 can accept allparameters and characteristics that the system 200 can detect relatingto interference. For example, the I/F mitigation control module 232 canaccept input from the I/F profiler 236, from the I/F estimator 222 andthe I/F sensor/detection subsystem 210, and can generate and send one ormore interference mitigation control signals to the DRS 201. As statedabove, knowing as much as possible about the interference causing datarecovery problems in the DRS 201 allows the I/F mitigation controlmodule 232 to tailor one or more solution(s) via control commands. Ifthe parameters provided by systems 210 and 222 degrade after suchcontrol commands are issued, the I/F mitigation control module 232 canrecognize such a less than perfect control response and attempt othercombinations of control signals. The system can iterate until theinterference problem is mitigated.

The I/F profiler 236 can monitor the outputs of the I/F sensor/detectionmodule 210 and the profiler 236 can utilize the outputs to create aprofile defining and quantifying the detected interference. If aninterference profile cannot be matched to a standard profile related toa specific communication standard, the detected interference profile canbe created and stored as an “interference signature” in the library. Theinterference signature can define what detection data is created by thesystem 200. If a determined signature can be matched to a standardprofile, a specific set of control signals can be provided by thelibrary to the I/F mitigation control module 232, and such instructionscan be applied to the DRS 201.

The I/F mitigation control module 232 can also include artificialintelligence, and can create links and assign weights to links betweeninterference data and control commands that successfully mitigateinterference. A link between an interference signature and a successfulcontrol configuration can achieve a greater weighting every time it issuccessful. In some embodiments, a user can set the links in the I/Fmitigation control module 232 such that the existence of one or moredetected interference parameters on the input of the I/F mitigationcontrol module 232 triggers the I/F mitigation control module 232 tosend a specific control signal or a sequence of control signals to theDRS 201.

Although only one line is drawn between the I/F mitigation controlmodule 232 and the DRS 201, as is illustrated in FIG. 1, it is intendedthat the I/F mitigation control module 232 can invoke an interferencemitigation method or subsystem at every stage or component of the DRS201. Such control at so many locations within the DRS 201 allows forcustomized solutions for a specific type of interference. Suchcomprehensive detection and control can allow the DRS 201 to operateflawlessly in the presence of significant interference.

Even when a match does not occur, the I/F profiler 236 can store aprofile for a detected interference occurrence. If the source of theinterference causes interferences to reappear, the I/F profiler can senda repeat offender signal to the I/F mitigation control module 232. TheI/F mitigation control module 232 can invoke the same control commandsevery time the repeat offender interferes. Some interferingcommunication systems transmit for short time durations over consecutivetime periods. When the profiler 236 determines that the interference isactive and present, the future periodic interference can be anticipated,and such anticipation can continue until the profiler determines thatthe interferer or interference is no longer present.

The I/F profiler 236 can utilize a template of timing standards fromlibrary 236 to improve the accuracy of predicting future bursttransmissions. In accordance with known time division standards andknown past start times of previous burst interferences, the I/F profiler236 can provide an expected time of arrival of the next burstinterference to the I/F mitigation control module 232.

The profiler 236 can provide basic timing control information to the I/Fmitigation control module 232. The profiler 236 can send informationindicating that an interference of a particular duration is occurring ona periodic basis. Additionally, the profiler 236 can indicate when anext burst is expected (possibly in real time) and a time till burstprediction or a predicted time interval between the bursts. As statedabove, communication standards dictate the length of a timeslot(s) andthe transmit and receive timing and durations.

Accurately determining a start time, burst duration and time periodbetween bursts can allow for improved control commands from the I/Fmitigation control module 232. Such control signals can be utilized byhigher level functions, where the control of an individual module in theDRS 201 can occur simultaneously with the onset of the interference. Acomprehensive library of time domain profiles can increase thepossibility that the I/F profiler 236 can match profile data receivedfrom the I/F sensors sub system 210 with a protocol standard such as aGSM in the library.

As stated above, the I/F mitigation control module 232 can acceptinterference related data from a plurality of sensors/sources and acceptinput from the I/F profiler 236 that further or more accurately definesthe interference and its characteristics. The I/F mitigation controlmodule 232 can use all of the inputs to make a decision regarding thebest mitigation technique available and generates a specific combinationof control signals to alter operation of the DRS 201. For example, theI/F mitigation control module 232 may activate or deactivate a powerconservation subsystem, clamp the gain on a VGA, activate components inan interference estimation system, activate components in aninterference cancellation system, activate or deactivate an active orstandard filtering system, and shut off all interference mitigationsystems.

In some embodiments, in response to specific input from the I/F detectorsensor module 210 and the profiler 236 the I/F mitigation control module232 may invoke a recursive interference estimation system, activate allinterference mitigation sub-systems, activate or deactivate any numberof mitigation sub-systems or other data recovery sub systems, activatetime domain or frequency systems and instruct the DRS 201 to changecommunication frequencies. All of the controls may only be activated ordeactivated for a short time period, particularly when interferencebursts are detected.

In some embodiments, the I/F mitigation control module 232 can determinethat the system 200 is experiencing more than one type of interferenceand invoke control commands that are mutually exclusive for each type ofinterference. The disclosed arrangements can select a low complexity,low latency interference mitigation technique. Cancellation techniquesgenerally do not degrade the desired signal so if signal levels are lowa cancellation technique can be selected as a tailored interferencemitigation solution.

Antenna 202 can represent multiple antennas having different locations.The spatial separation of the antennas and the different communicationpaths created between the interfering transmitter and the transmitter ofthe desired signal allows the phase detector 225 to determine differentphase relationships between the desired signal and interfering signalsat each antenna/receiver. The detected phase differences can be utilizedby the I/F estimator 222 to assist in estimating the interference. Insome embodiments the phase detector 225 could be part of the I/Fdetector sensor module 210 and could send data directly to the I/Fmitigation control module 232 and the I/F profiler 236.

The spatial separation of the antennas and the different communicationpaths created between the interfering transmitter and the transmitter ofthe desired signal can create a phase difference between theinterference and desired signals as seen by the antennas of thereceiving system. Phase shifters in one or both paths can then be usedto adjust the phases so that the phase of the two interfering componentsis 180 degrees out of phase while the phase of the desired signalcomponents is not 180 degrees out of phase. Linear summation of the twosignal paths then allows cancellation of the interference while leavinga virtually unchanged desired signal. However, detecting phasedifferences requires multiple receiver chains and creates additionalinefficiencies such as increased costs and power consumption.

The system can have a first in first out (FIFO) type buffer memory todelay the incoming data until an interference estimate is made by theestimator 222. The buffer will introduce some latency, although such adelay is not significant with respect to the latency permitted by theWLAN protocol. The disclosed arrangements are not limited to anyparticular wireless protocol or system such as an 802.11 compliant WLANsystem, but the disclosed embodiments could be utilized by many othercommunication systems.

In some embodiments, the system 200 can include a detector that isspecific to an interference that causes serious problems. One suchexample would be a global system for mobile communications (GSM)interference detector. Such a detection system could be specificallydesigned to detect specific types of interference such as narrow bandpulsed interference from a GSM device. The narrow band detection subsystem can be connected close to the RF input and can detectinterference up stream or prior to packet detection. This specializeddetection system can have an electromagnetic spectrum sensing module.The specialized interference detection sub system can have detectioncomponents that are tuned or tailored to detect GSM interference. Inresponse to such detection, the specialized subsystem can disallowpacket dropping and could disable the PCC or sleep mode sub system whenthe amount of received energy changes in certain circumstances. Such aspecialized detection and control system can avoid restarts andre-synchronization functions caused by falsely determining that powerlevels are below a specified limit.

In some embodiments, the energy detection system can be deactivated forthe duration of a packet once beginning of the incoming packet isdetected. It can be appreciated that when the disclosed system receivesinterference that changes the power level in the receiver by more than apredefined level, the system 300 can be deactivated by a powerconservation system and prevent the system from entering a sleep mode,allowing the receiver to detect the wideband data packets that arriveduring and subsequent to the interference burst.

The disclosed interference identification/mitigation system 200 couldsupport most wireless technologies including wireless handsets such ascellular devices, or hand held computing devices that utilize WLAN,WMAN, WPAN WiMAX or handheld digital video broadcast systems (DVB-H).The system 200 is also compatible with single antenna or multipleantenna systems such as multiple input multiple output systems (MIMO).

Referring to FIG. 3, a portion of a narrow band interference detectionsystem 300 is depicted. The sub band detection system 300 could beimplemented as the interference bandwidth detector 218 in the systemdescribed in FIG. 2. The system 300 can include a sub band divider orband splitter 304, four sub band filters (SBF) 306, 308, 310, and 312,four energy level (E/L) detectors 314, 316, 318, and 320, a comparemodule 324, a reference level module 322, a time domain cancellationmodule 326, a power conservation module 330 and a narrow bandinterference mitigation module 328. The system 300 can also include acontrol output 333 that can be utilized to control various sub systems.

In operation, the system 300 can accept radio frequency (RF) input 302utilizing a band splitter 304. The band splitter 304 can divide theelectromagnetic energy on the RF input 302 into different paths. In someembodiments, the band splitter 304 can have mixers or parallelconductors that can separate the RF energy into various frequency rangesor sub bands. In some embodiments, the band splitter 304 can be asplitter or a divider that couples the RF input 302 to multiple outputs.In some embodiments, each sub-band signal out of the band splitter canbe provided to a band pass filter, such as filters 306, 308, 310 and312.

The filters 306-312 can be designed to reject at least one sub band orto pass at least one sub band. Such a configuration allows the energy ina specific sub band to pass to the output of the filter largelyunaltered. The unaltered signal can be utilized as a detection mechanismindicating interference that is occurring in a specific frequency rangeor sub band. Band pass, band rejection, band limit, notch, T-notch, bandelimination and band rejection filters in the proper configuration canbe utilized to pass or convey a specific band or sub band of frequencieslargely unaltered. However, the filters 306-312 can attenuateelectromagnetic energy having frequencies in a specific range to lowerenergy levels.

When filters 306-312 are implemented as band pass filters, they can bedesigned with a narrow (small band) of frequencies that do not getattenuated, and all frequencies out of the sub band are significantlyattenuated. A filter with a narrow frequency rejection range and a sharproll off is often referred to as a filter with a high Q factor. Filters306-312 can have an order of six, which is a relatively high order.Generally, the higher the order of the filter, the greater the rate ofattenuation as the frequency moves out of the pass band. Alternativelystated, the higher the Q factor the narrower the band pass region andthe greater the attenuation of the energy at the filter's “edges” or theedges of the band pass. For example, a filter with an order of six canprovide a significant increase in attenuation with a nominal increase infrequency (a steep slope when frequency and attenuation are graphed).

Generally, filters 306-312 can pass the electromagnetic energy of the RFinput 302 to their output based on the tuning of the filter and thefrequency of the electromagnetic energy applied to the input of thefilter. The energy in a specific sub-band that is passed by a filter canbe provided to the respective energy level detectors 314-320. Energylevel detectors 314-320 can detect the energy level (or a relativeenergy level) that is present in each sub-band. The energy output fromthe energy level detectors 314-320 can be provided to the energy levelcompare module 324. The energy level compare module 324 can compare theenergy levels present in each sub-band and obtain relative power leveldifferences for each sub band. When a sub band energy level on the inputof the compare module 322 equals or exceeds the trip point set by thereference level, the compare module 324 can assert a signal on itsoutput indicating a relatively high level of noise in the sub band.

In some embodiments, a user can set the value of the reference level 322trip point to the amount of energy required by a sub-band and can setlevels that, when detected between a band and an average energy level,can activate the output signal of the compare module 324. The referencelevel module 322 can be controlled by a user and thus, the trip levelscan be user selectable.

In some embodiments, if the energy level detected for one sub-band (i.e.the output from one detector 314-320) is higher than the energy level inthe other three sub-bands by a predetermined threshold value, (ascontrolled by the reference level 322) the compare module 324 can assertan output signal that indicates that narrowband interference has beendetected. In other embodiments, the output signal can be asserted when asub band contains an energy level that is a predetermined amount greaterthat the average energy level of all sub bands.

The activated control signal can be utilized to activate a narrowbandinterference mitigation sub-system such as narrowband interferencemitigation module 328. When such a sub-system is activated, moduleswithin the system such as a variable gain amplifier can be controlled oradjusted such that the narrowband interference does not significantlyinterrupt a communication session.

In some embodiments, the sub band with a high energy level generallyindicates that the sub band shares a frequency with a side band of adifferent communication system. For example, the third harmonic oftransmitting GSM devices falls within sub bands of an 802.11 compliantsystem. The disclosed system 300 can determine with some accuracy, (withthe assistance of other detecting sub systems and profiles in a libraryas illustrated by FIG. 2), the frequency of the interfering signal.

In some embodiments, the received interference on the RF input 302 canhave frequencies that are sufficiently broad that the interference willmanifest at the output of more than one sub band filter. In otherembodiments, the received interference may have a frequency that is onthe border between two sub-band frequencies. Such border linefrequencies can also manifest at the output of two adjacent sub bandfilters that pass adjacent frequencies.

When two energy level detectors that are frequency adjacent detectenergy levels that are higher than the other energy levels in otherdetectors by a predetermined threshold level, the compare module 324 cangenerate a control signal indicating that narrowband interference ispresent. In some embodiments, the control signal can indicatespecifically that two sub bands are experiencing relatively high levelsof energy. Some interference mitigation sub systems can utilize thecontrol signals that provide this additional resolution to activatedifferent types of interference mitigation arrangements. It can beappreciated that the different types of interference detection can beutilized to activate different interference mitigation sub-systems. Thenumerous types of control signals and the numerous types of interferencesub-systems and techniques allow the system to tailor a solution basedon the characteristics of the interference.

The detection systems disclosed can provide specialized control commandsto specialized interference mitigation sub systems. Such a comprehensivedetection mitigation system allows a receiver to operate efficientlyduring high levels of interference. One reason for such efficiency isthat an appropriate interference mitigation system can be activatedbased on one or many characteristics of the interference.

In some embodiments, when the difference in energy levels between onesub band and all other sub bands is less than the threshold value, someor all interference mitigating sub-systems or functions can bedeactivated. Such a deactivation can allow for a more robust signal toreach the data recovery portion of the system because filtering andcancelling on low levels of interference can degrade signal quality.Accordingly, different from traditional systems, the detection ofnarrowband interference by the detection system 300 allows aninterference mitigation system to distinguish between an absence of WLANtransmission activity and a situation where narrowband interference ismasking WLAN transmissions.

In traditional WLAN systems, masked WLAN transmission would commence asleep mode for the system. The output of the compare module 324 candeactivate the power conservation module 330 when narrowbandinterference is detected such that the system will continue receivingand processing data when the system is receiving high levels ofinterference. In some embodiments, the compare module 324 can determineor estimate a signal to noise ratio, and this ratio can be comparedagainst a predetermined threshold to make high level mitigationdecisions.

In other embodiments, time domain based interference can create a pulseat the output of the compare module 324. The time domain cancellationmodule 326 can detect such a periodic switch at the output of thecompare module and generate a control signal indicating that theinterference is periodic in nature. Responsive to such detection, thetime domain cancellation module 326 can activate one or more time domaincancellation subsystems (not shown).

Further, it can be appreciated that the system 300 can be utilized tomake decisions on what kind of interference mitigation to implement. Forexample, the signal could be utilized to enable or disable variouslevels of computational interference and cancellation algorithms basedon the intensity and type of interference detected by the system. Inother embodiments, other interference mitigation sub-systems can bedeactivated when they are not providing beneficial results. Thedisclosed detection system 300 is more economical than traditionalsystems because only a single signal path (front end) is required todetect interference and the desired signal. Further, only a single downconverter and single ADC are required to achieve data recovery.

In the absence of interference and any desired signal, the energy levelof each of the sub bands should be relatively equal. However, whennarrowband interference is present on one or more of the sub bands, suchinterference will exhibit a greater energy level on one or moresub-bands. In contrast, in the presence of only the desired signal withminimal interference, each sub-band will exhibit relatively the sameenergy level. The presence of narrowband interference alone can bereadily detected by the disclosed system. The detection of narrowbandinterference can be utilized to override various energy detectionsystems that activate power saving systems and can also be utilized toactivate and deactivate various interference mitigation systems. In someembodiments, deactivating the energy detector so that subsequent changesto the incoming energy are ignored can facilitate receiversynchronization and packet preamble detection.

The narrowband interference detection system 200 can be implemented with4 sub-band infinite impulse response rejection filters of order 6. Everyfilter can have a rejection bandwidth of ¼ of original spectrum, i.e. 5MHz for a WLAN narrowband detection system. Rejection sub-bands may ormay not overlap. The suppression level of each filter can beapproximately 40 dB.

Generally, FIG. 3 illustrates a block diagram for possible locations for306-312 filters in a WLAN processing chain. In another embodiment, aninput signal can initially be provided to the four sub-band filters306-312, and the power levels at the outputs of the four sub-bandfilters 306-312 can be compared. If one level is relatively lower thanthe three other filters, this can indicate the presence of narrowbandinterference. This can be important information for a system that isconducting a synchronization process as such information can beforwarded to the synchronization subsystem. These rejection filters306-312 can be used for detection and synchronization and for detectingthe presence of GSM based and/or other time based interference.

After detection of specific interference types such as GSM typeinterference is made, one of the filters can have a dual purpose. Thefilter that has the minimum level at its output can remain on while allother filters are switched off. This minimum level can provide a metricof the signal level available to the receiver. Providing the minimalenergy output level to all detection and synchronization units dictatesthat all detection and synchronization units will be provided with asignal containing only three quarters (¾) of the energy spectrum of theoriginal signal.

The output of the remaining filter will have a narrowband interferencethat is significantly reduced. It has been shown that the detection andsynchronization parts of a WLAN receiver are able to operate with theminimal energy level if the interference to signal ratio is less than20-25 dB. The detection system 300 can overcome the false detection ofan incoming packet caused by interference, and can allow correct packetdetection following the onset of narrowband interference. Simulationresults show an improvement from twenty percent (20%) correct packetdetection to near 100% correct packet detection in the presence ofnarrowband interference.

Referring to FIG. 4, a flow diagram 400 illustrating a method fordetecting interference, such as narrowband interference is disclosed.The interference detection method 400 could be utilized by theinterference bandwidth detector 218 described in FIG. 2. As illustratedby block 402, incoming signals can be divided into sub-bands. Asillustrated by block 404, the energy level for each sub-band can bedetected. At decision block 406, it can be determined if the energylevel of all sub bands is significantly lower than the energy level of asingle sub-band.

If the energy levels of all sub bands are substantially lower than theenergy level of one sub-band then, as illustrated by decision block 408,it can be determined if the energy of a single sub band is a higher thanall other sub bands by a predetermined amount. In some embodiments, thepredetermined amount is 3 dB and this predetermined level can be userselectable. If the single sub band has an energy level that is apredetermined amount greater than the other sub bands, interferencemitigation features can be activated, as illustrated by block 418. Afterthe interference mitigation is activated the process can end. If, atdecision block 408, the energy level of the single sub band is notgreater than the energy level of the other sub bands by thepredetermined amount, then one or more interference mitigation featurescan be deactivated, as illustrated by block 424.

Referring back to decision block 406, if either no sub bands or morethan one sub bands have high energy levels, then as illustrated bydecision block 414, it can be determined if the energy level for two subbands is higher than all other sub bands by a predetermined amount. Insome embodiments, the predetermined amount can be 3 dB. If the energylevel in the two sub bands is less than the predetermined amount, thenas illustrated by block 424, one or more interference mitigationfeatures can be deactivated due to the lack of interference.Deactivating mitigation features in the absence of interference canallow a data recovery system to operate with lower data error rates.

At decision block 414, if it is determined that the energy level of thetwo sub bands is higher than the remaining sub bands by a predeterminedamount, then as illustrated by decision block 416, it can be determinedif the two sub bands with the higher energy levels are assigned toadjacent frequency ranges. If the two sub-bands are not adjacent infrequency range then interference mitigation features can be activatedas illustrated by block 418.

If, at decision block 416, it is determined that the two sub-bands withhigher energy levels are adjacent, then as illustrated by decision block420, it can be determined if the energy levels of the two sub bands arehigher than the energy level of all remaining bands by a predeterminevalue. If they are not, then one or more interference mitigationfeatures can be deactivated, as illustrated by block 424. Deactivationof interference mitigation features can increase the efficiency andreliability of a communication system when interference levels are belowa certain parameter. Such low levels can be determined by the disclosedsub band energy level detector method.

If the two sub bands with higher energy levels have energy levels abovethe remaining sub bands by a predetermined value, then interferencecancellation functions can be activated as illustrated by block 422. Theprocess can end thereafter. Accordingly, interference mitigationsub-systems can be activated and deactivated base on the magnitude andbandwidth of the interference. Further, cancellation type interferencemitigation systems can be activated and deactivated based on themagnitude of narrowband interference.

Referring to FIG. 5, a flow diagram 500 illustrating a method forpredicting burst interference is depicted. As illustrated by block 504,it can be determined if a predetermined level of narrowband interferencehas been detected. If the narrowband interference level is less than thepredetermined value the process can end. If narrowband interference canbe detected that has an energy level that is greater than thepredetermined value, then a timer can be started. The timer can bestarted when the interference is detected or when the interferencearrives, as illustrated by block 506. Characteristics of theinterference can be detected, monitored and stored by the system.

The system can continue to monitor the interference and at decisionblock 508 it can be determined if the interference has subsided below apredetermined level. If the interference has not subsided below thepredetermined level after a predetermined amount of time, it can bedetermined that the interference is not burst interference or periodicinterference and the process can end.

The narrowband interference detection system can be synchronized toperiodic interference using learned and predetermined timingcharacteristics of burst interference. Thus, the system can sample theinterference levels during the transmit period (i.e. a sample period) ofthe interfering device. Sampling the sub band filter outputs at presetsampling times allows the system to determine whether the periodicinterference has subsided or is continuing. The energy sampling systemcan have a timer. The timer can be set to the cycle time of thetransmitter and can be activated when a burst is initially detected.When the timer times out, the timer can send a signal indicating thestart of the next interfering signal.

A sampling period can be set for just before the interference isexpected and end just after the duration of the transmit pulse. If theinterference starts at this time, and the sampling system detects theinterference, the interference can be “re-identified” as a knownperiodic interference. If the interference does not appear during thesampling time or during the expected interval even though suppression ofmitigation mechanisms have been activated, the detection system candetermine that the interference should not be anticipated anymore.

If at decision block 508 the interference subsides, then as illustratedby block 509 the timer can be stopped. The start time and stop time ofthe detected interference can dictate the duration of the interferingtransmission. Such timing data is accurate and essential to devicesutilizing a time domain configuration to communicate. One such commontime domain technology is time division multiple access technology(TDMA). As illustrated by block 510, a burst interference profile can becreated using the acquired timing data. The acquired timing data caninclude the start time and the stop time or the duration of the pulse.The acquired data can also include the interference frequency(ies), themagnitude of the interference and other characteristics of theinterference.

As illustrated by decision block 512, the burst interference profile canbe compared to standard or created profiles in a library or a look uptable. The system can create profiles based on past interferences andsuch learned profiles can be stored with the standard profiles. If thecreated profile “matches” or has enough similar characteristics to thestandard profile, it can be assumed that the interference matches aknown profile and comes from a device conforming to a communicationstandard. This assumption allows the system to acquire additionalcharacteristics about the interference such as when the interferenceshould be expected. A set of control commands can be associated with andstored with the standard profile in the library. If the created profilefinds an acceptable match in the library, as illustrated by block 514,periodic interference mitigation control commands can be retrieved fromthe library and assigned to a profiled interference. Such controlcommands can be utilized to control the interference mitigation portionof the communication system.

The associated control commands can be tailored to adjust specificfunctions of the data recovery system such that the system can mitigatethe interference. Generally, a device that is transmitting aninterfering signal to a data recovery system is transmitting inaccordance with a particular communication standard. Applying a standardremedy or standardized control signal to an identified problem can provean efficient mitigation method. Significant data about the interferencecan be stored by the data recovery system and such data can be utilizedto control interference mitigation in the affected device. For example,the interference frequency, the duration of each transmitted pulse, thecycle time, or burst interval and other data can be located and utilizedto mitigate present and future interference.

As illustrated by decision block 516, it can be determined if theprofiled interference occurs in subsequent periods in accordance withthe assigned control data. If the interference occurs or can be detectedin subsequent periods, the control signal can continue to be implementedas the process reiterates to block 514. As illustrated by decision block516, if the profiled interference cannot be detected in subsequent timeperiods then the process can end.

Referring back to decision block 512, if the system cannot find aninterference profile that sufficiently matches a profile in the library,then as illustrated in decision block 518, it can be determined if asubsequent interfering pulse with the same or a similar profile can bedetected. If a subsequent pulsed interference with a similar profilecannot be detected the process can end. If a subsequent pulse with thesame or similar characteristics or profile can be detected, asillustrated by block 520, a new profile can be stored in the library.The profile can include a start time, duration, a stop time, a period, afrequency and a magnitude. As illustrated by block 522, control signalscan be created that are tailored to mitigate interference problemsassociated with the narrowband burst interference that was profiled. Asillustrated by decision block 516, as long as the interference ispresent in consecutive time periods the control signal in the librarycan be applied as the method iterates to block 514. When theinterference subsides the process can end.

Referring to FIG. 6, a flow diagram 600 illustrating a method fordetecting timing parameters of burst interference is illustrated.Typical time domain based transmissions create burst interference orperiodic interference to other devices. Such burst interferencestypically have a predictable burst duration and cycle time, based on theframe length and time allocation for the device. The disclosed methodcan acquire parameters of narrowband interference and can send a signalto an interference mitigation system based on the results ofinterference sampling intervals. When the sampling intervals continue todetect bursts of interference, the system can assume that there will beinterference during a future transmission time slot.

As illustrated by block 602, the environment can be sampled to determinelevels of interference in numerous sub bands. At decision block 604burst interference can be expected and it can be determined if timedomain narrowband interference above a predetermined level is detectedin a sub band. If the time domain narrowband interference is notdetected it can be determined if such interference was anticipated basedon prior interference, as illustrated by decision block 606.

If the interference was not anticipated, the system can operatenormally, as illustrated in block 608. The process can end thereafter.If at decision block 606 the detected interference was anticipated, theanticipation features of the system can be disabled as illustrated byblock 610. The process can end thereafter.

Referring back to decision block 604, if time domain narrowbandinterference is detected in a sub band then, as illustrated in decisionblock 612, it can be determined if the periodic interference has beenpreviously identified. A timer can be utilized to detect time intervalsbetween interference bursts and to predict a start of the next burstinterference. If the interference starts at the predicted time in block604, it might be identified as the periodic interference that hasoccurred in the past as in decision block 612. If the interference doesnot appear at the time expected as in block 606, the method can indicatethat the interference has subsided and should not be anticipated in thefuture by disabling the interference anticipation features.

If the interference has been previously identified, preemptiveinterference mitigation can continue as illustrated by block 614. Thepreemption can be a periodic signal that maintains a particular gainsetting for variable gain amplified during a burst of interference. Suchcontrol can keep a receiver in a dynamic operating range in the presenceof periodic narrowband interference. Such a preemptive signal can beasserted throughout the period of the interference and possiblythroughout packet reception. Scheduled interference mitigation can be apreemption process. Previously identified interference can haveinterference levels, a period, duration, start times and end times ofthe interference so that the preemptive mitigation can be started andended at correct times while providing the appropriate interferencemitigation levels.

The process can end thereafter. Referring back to decision block 612, ifthe interference has not been previously identified then, as illustratedby block 616, the characteristics of the interference can be stored. Asillustrated by block 618, the parameters can be compared to parametersresulting from known communication standards.

As illustrated by decision block 620, if the interference does notrepeat on a periodic basis the process can end. If the interferencerepeats on a periodic basis, an interference mitigation control profile622 that can include control characteristics, can be created, stored andretrieved to control a data recovery system during future periodicinterference. The process can end thereafter.

In some embodiments, system memory can provide a library of pre-loadedinterference profiles where the profiles represent specific types ofknown interference. In some embodiments, the library can be loaded withsuch interference profiles as the system learns different reoccurringpatterns from devices from a particular manufacturer. The interferencecharacteristics and patterns can also be acquired from devices thatoperate according to a particular communication standard. Thus, thedigital samples acquired by the sampling module or an output of an ADCand the digital samples can be compared to a library of samples. Aftercomparing a “match” or similarities between the detected interferenceand a known or past interference, an interference signature can be made.As a result of the match, a tailored control signal can be located andsent to an interference mitigation sub system such as a powerconservation controller, an interference mitigation module or afrequency domain processing system. The control signals that areselected can be based on the success of previous mitigation techniques.

Comparing a stored signature to a detected signature can be timesensitive, as the data points representing amplitude, phase, etc. andtheir relative timing can be compared to stored interference signatures.Generally, an interfering device will have an interference profilesignature both in timing and in digital value and this profile willproduce a percentage of data points that will be the same for eachinterfering transmission from the interfering device. Thus, thesignature can provide points that can be compared to previously storedtiming based data points.

In some embodiments, the sampling module can empirically determine aninterference signature of a transmitting device. The signature can havea start time, duration, a duty cycle and periodicity among other things.Comprehensive interference detection and control signals tailored tosuch accurate detection can have a single receive path and can providehigh data throughput in the presence of narrowband interference andnarrowband burst interference.

Referring generally to FIG. 7 a time domain interference cancellationsmethod is disclosed. As a result of the increasingly crowded frequencyspectrum, it is not unusual for communications systems to receiveinterference from another man made communication device. As statedabove, a challenging situation occurs when interference is received by awideband WLAN receiver due to the emission of a third harmonic of anearby GSM compatible cell phone. One or more frequencies of atransmitting GSM compatible device have a relatively high power leveland fall within the band of frequencies utilized by the victim receiver.This interference cannot be effectively removed utilizing filteringtechniques because the desired signal can be adversely affected byfiltering.

In accordance with the description of FIG. 7 an alternative method isdisclosed that performs interference cancellation in which an inverted“replica” or estimation of the interference is added to the signalreceived by the victim receiver. If the inverted signal is exactlymatched in amplitude and is opposite in phase with that of theinterference received, then the interference can be almost “completely”cancelled without affecting the integrity of the desired signal. Thereplica of the desired signal can, in some cases be derived by focusingon receiving signals from the interfering transmitter and quantifyingthese signals. Accurate sampling is possible if the aggressor and thevictim are located on the same platform.

Another alternative cancellation technique utilizes multiple antennasand receive paths. The spatial separation of the antennas and thedifferent communication paths can be utilized to determine differentphase relationships between the desired signal and interfering signalsat each antenna/receiver. These phase difference can be utilized tocancel the interference signal with only minor change to the desiredsignal. This technique which requires multiple antennas and receivepaths is less efficient that the technique disclosed by FIG. 7 becauseof the increased costs and power consumption associated with suchtechniques.

In yet another traditional interference cancellation method a WLANreceiver can be designed with a sufficient dynamic range such that a“perfect” or accurate representation of the interference signal can bederived and then utilized to cancel the interference component of thereceived signal. However, practical considerations such as circuit boardarea, cost and power consumption limit the dynamic range of mostreceiver designs. FIG. 7 below describes a number of techniques that canbe applied by a receiver to enhance the performance of the interferencecancellation embodiments.

The method described with reference to FIG. 7 generates a mathematicalequation that is a “replica” or an estimation of the interference signalcan prove more economical for extracting a desired signal from a noisefilled environment. Unlike noise interference from most man made sourcesinterference from communications systems can be defined in the timedomain by relatively simple mathematical expressions such as apolynomial. An interference estimate provided by a polynomial can beobtained by solving a set of simultaneous equations where the equationscan be derived from a plurality of series or time samples of theinterference waveform.

FIG. 7, is a flow diagram 700 describing a method that can estimate theinterference portion of a received signal, subtract the interferenceportion from the received signal and provide a data signal that hasgreatly reduced interference levels to a data recovery system. Althoughthe disclosed embodiment describes processing a single OFDM symbol, theteaching herein could be utilized to mitigate interference for anywideband time domain signal. In addition, processing a single symbol isdisclosed however, numerous symbols could be processed simultaneouslyutilizing the described features.

The disclosed method utilizes the tendency that narrowband interferencehas a much higher energy level than the level of the desired signal.Thus the interference is easy to detect and process. High levels of “inband” interference can seriously degrade the performance of broadbandcommunications systems. While filtering techniques can be used to removesome interference, filtering can cause a loss of signal and loss ofdata. This occurs because filtering removes part of the desired signal.Cancellation techniques can overcome the limitation of filtering butrequire an accurate replication of the interference so that theinterference replication can be subtracted from the received signal toprovide a desired data laden signal with a low level of interference.The method described by FIG. 7 can estimate the narrowband interferencein the time domain.

As illustrated by block 701, an OFDM signal with interference can bereceived. As illustrated by block 702, the difference frequency (w)between interference carrier frequency and the OFDM symbol frequency(the desired signal) can be determined. The received signal can be downconverted utilizing the difference frequency (w), as illustrated byblock 704. In some embodiments, the desired signal can be filtered fromthe received signal to isolate the interfering signal and providesampled data points that represent a more accurate representation of theinterfering portion of the signal than solely with the received signal.The disclosed method is not limited to OFDM symbols and could beutilized for narrow band interference cancellation for any widebandreceiver. The digital data can be sampled and the estimation can be madesuch that the higher frequency component of the desired signal isignored and the lower frequency of the interfering signal can becomemore pronounced. The results of the down conversion can be multiplied bya pseudo inverse of a Vandermonde matrix, as illustrated by block 706.

The digital data points representing the received interference can beutilized to estimate the interference. In some embodiments a fourthorder polynomial equation such as . . . At⁴+Bt³+Ct²+Dt+E can beutilized. The parameters A, B, C, D, and E can be estimated/determinedusing many different interpolation techniques such as a least squarestechnique that attempts to minimize the sum of the squares of thedistances between the data points that are utilized to create the curveand such an interpolation technique generally “connects” thedistribution of data points with an equation describing a line. One suchtechnique is to utilize a Vandermonde matrix to perform a least squaresapproximation on the sample data. Stated in an alternate way, theVandermonde matrix can yield a polynomial equation having a leastsquares fitting to reconstruct the interference waveform from thedistribution of the data points.

It can be appreciated that there can be a tradeoff between having a“perfect fit” requiring a significant number of computations andcreating a smooth well-behaved function or line with a sufficientaccuracy and a nominal amount of computations. It has been determinedthat a fourth order polynomial can provide adequate accuracy with amanageable number of computations. However, a fourth order polynomial isnot a limiting factor as higher and lower orders could be utilizedwithout departing from the scope of the present disclosure. Whenutilizing a fourth order polynomial to estimate the interference beingreceived by an 802.11 compliant WLAN, the size of the Vandermonde matrixis 64×5.

Generally, the more data points available for the interpolation, thehigher the degree of the polynomial that can be utilized and the greateroscillations the estimation or function will exhibit between the datapoints. Therefore, a high-degree interpolation may be a poor predictorof the function between points, although the accuracy at the data pointscan be “perfect.” The least squares approximation can sample theinterference frequency and convert the interference frequency to a verylow frequency. Such a transfer provides a smooth function that is fittedto the received signal (i.e. data plus interference). The fitted signalwill indicate that the interference has a much lower frequency than themodulated data. The modulated data will have a rapidly changing signallevel with a much lower amplitude than the interference.

The Vandermonde matrix is a matrix with the monomial terms of ageometric progression in each row. The Vandermonde matrix is useful inpolynomial interpolation or a mathematical formula to calculate valuesbetween two data values. A Vandermonde matrix generally solves a systemof linear equations to find the coefficients of the polynomial where thepolynomial describes the data. The Vandermonde matrix can be expressedas follows where t represents time:

${V = \begin{bmatrix}1 & t_{1} & t_{1}^{2} & t_{1}^{3} & t_{1}^{4} \\1 & t_{2} & t_{2}^{2} & t_{2}^{3} & t_{2}^{4} \\1 & t_{3} & t_{3}^{2} & t_{3}^{3} & t_{3}^{4} \\... & ... & ... & ... & ... \\1 & t_{N} & t_{N}^{2} & t_{N}^{3} & t_{N}^{4}\end{bmatrix}},$

and the vector for the noise component “p” can be expressed withpolynomial coefficients as follows:

${p = \begin{bmatrix}E \\D \\C \\B \\A\end{bmatrix}},\mspace{14mu}{and}$

and the data vector “y” containing the OFDM symbol can be described as

$y = {\begin{bmatrix}y_{1} \\y_{2} \\y_{3} \\... \\y_{N}\end{bmatrix}.}$

An inverse or pseudo inverse of the Vandermonde matrix V′ can bedetermined. The pseudo inverse of the Vandermonde matrix can have someproperties of the inverse matrix but not necessarily all of theproperties. The interference can be estimated utilizing a least squaresapproach by multiplying the data vector, y, by the pseudo inverse of theVandermonde matrix V′, such that p=V′(y), as illustrated by block 706.It can be appreciated that the Vandermonde matrix V will be the same foreach OFDM symbol and thus, the inverse of the Vandermonde matrix onlyneeds to be calculated once.

Accordingly, the resulting interference vector “p” as calculated inblock 706 can be utilized to estimate of the interference by executingthe equation y=(V)p or by multiplying the Vandermonde matrix to thesignal vector component, as illustrated by block 708. Accordingly, thenoise component vector “p” as determined by the digitized data can bemultiplied by the Vandermonde matrix to provide the desired signal “y”where V(p)=y.

The interference estimate can then be subtracted from the OFDM symbol tocreate a corrected OFDM signal. Thus, the estimated interference resultof block 708 can be subtracted from the received signal as illustratedby block 710. The received signal can be digitized and stored in a firstin first out buffer and thus can be delayed while the interferencecancellation equation is generated and the interference is cancelled.After subtracting the estimated noise from the actual signal a signalwith insignificant interference can be provided for data recovery. Theresult can be up converted by the difference frequency, as illustratedby block 712. After up conversion the symbol can be extracted from theprocessed input symbol, as illustrated by block 714. In the case of theWLAN receiver, the interference can be estimated for each channel or foreach orthogonal frequency division multiplexing (OFDM) symbol.Accordingly, the interference for each OFDM symbol or each channel canbe cancelled in a parallel process. The process can end thereafter.

In accordance with the present disclosure, the arrangements disclosedherein can utilize time domain cancellation techniques when high levelsof interference are present in a receiver. Such time domain cancellationcan be performed without requiring cross modulation of the noise signalwith the signal having the noise and the desired signal. Thus, thedisclosed time domain cancellation techniques can avoid problemsassociated with transforming the incoming signal into the frequencydomain.

The disclosed time domain cancellation can acquire a replication (with aspecific degree of accuracy) of the received interference and subtractthis replication of the interference from the received signal which hasthe combined signal of interference and the desired signal. At lowinterference to signal ratios, such time domain cancellation may beunnecessary. This is because correct demodulation of the desired lowinterference signal may be possible without requiring a subtraction ofthe noise component. The disclosed arrangements can be considered as ablind time domain cancellation technique. Such a blind technique canutilize a noise detector that can activate and deactivate noisesuppression or noise cancellation features

Simulations for GSM 3rd harmonic interference power having a magnitudeof between 1-28 dB larger than WLAN signal power and carrier frequency3-7.8 MHz larger than the WLAN carrier frequency was performed using thetime domain mitigation algorithm with the polynomial approximation ofthe interference. The interference mitigation system was able to correctthe cyclic redundancy check (CRC) of the WLAN packets even when theinterference power level was 26-28 dB greater than the desired signal.

Referring to FIG. 8, a flow diagram 800 illustrating a method forcancelling interference is depicted. The method can receive a signal andsample each symbol as illustrated by block 802. As illustrated bydecision block 804, it can be determined if narrowband interferenceexists in the received signal that has an energy level that issignificantly greater than the desired signal. If there is not, theprocess can end. However, if narrowband interference is present withenergy levels that are significantly higher than the signal level, thereceived signal component or signal vector component can be downconverted, as illustrated by block 806.

As illustrated by block 808, an estimate of the interference can be madeby generating a polynomial equation where a smooth curve is generatedbased on data samples of the received signals. Such a configuration isillustrated graphically in FIG. 9. The equation can be “transferred” tomathematically create a frequency that is magnitudes lower than thesignaling frequencies, the frequency(ies) that carry the desired signalor the signal vector component. Thus, the equation can describe a smoothfunction or linear function that is fitted to an area occupied by theaverage values created by a digitized version of the received signal.The received signal would include the data vector component portion ofthe signal and the interference component of the signal.

The interference estimate equation or fitted equation generallyrepresents the interference portion of the received signal because thedata portion of the signal is a rapidly changing signal and has asignificantly lower amplitude than the interference portion of thesignal. Thus, an equation that represents the data would have relativelyconstant amplitude and a much higher frequency than the equationdescribing the interference. From the lower frequency smooth signal ananti-phase signal can be generated, as illustrated by block 810. Asillustrated by block 812, the anti-phase signal can be subtracted fromthe received signal for each symbol. As illustrated by block 814, theresults of the subtraction can be up converted and data can be recoveredfrom the resulting signal. The process can end thereafter.

Referring to FIG. 9, a graph with two sampled functions 902 and 904 isdepicted. Function 902 frequently oscillates high and low around a lowerfrequency function 904. The lower frequency function starts at the upperleft of the graph at a high value and ends in the lower right corner ofthe graph as a low value. Function 902 represents an example of apossible OFDM symbol or signal component with an interference component.Function 904 represents an example of an interfering component of areceived signal. The graph illustrates where the interfering component904 has been estimated utilizing digitized data from the received signaland a least squares estimation using a fourth order polynomial equationand the Vandermonde matrixes as describe above. Note the slow frequencyor slope of the noise and the higher frequency of the data.

Interference from a GSM based 3rd harmonic interference having a carrierfrequency from three to approximately eight MHz larger than the nominalWLAN carrier frequencies and power levels from one to twenty eightdecibels larger than nominal WLAN signal power was simulated. Thedisclosed time domain interference mitigation arrangements were able tocorrect the data errors of the WLAN packets when the interference levelwas between 26-28 dB above the signal level. Such levels depended on theinterference carrier frequency when a fourth order polynomial was usedto estimate the interference.

It can be appreciated that the noise estimation method described in FIG.9 is computationally simple compared with many other interferencecancellation techniques. Further, because the disclosed method onlyutilizes a single receive path to receive and process the desiredsignal, only a single front end receiver is required.

FIG. 10 is a graph of a waveform of the desired signal or aninterference mitigated signal after the interference has been subtractedfrom the received signal utilizing the estimated interference equationresulting in an improved or corrected OFDM symbol. Thus, the higherfrequency component of function 902 that oscillates above and below thelower frequency component of interference in FIG. 9 is easier for a datarecovery system to process without errors. It should be noted that thescale on FIG. 9 has increments that are over four times greater than thescale utilized in FIG. 10 and that the signal swing of the un-canceledsignal is much greater than the signal swing of the desired signal wheninterference is present.

Referring to FIG. 11, a flow diagram 1100 depicting an iterative methodfor estimating interference is disclosed. In some embodiments, timedomain narrowband interference can be detected and a polynomial equationestimating the noise component can be utilized in a subtraction processto cancel the noise signal. The equation can be generated using arecursive estimation process where the error that results in theinterference mitigated signal can be utilized in the next iteration toreduce the error in the estimation.

As illustrated by block 1101, during an initialization process, thenumber of desired iterations can be selected by assigning the number ofiterations desired, X to N, as N=X. Generally, the larger the number ofiterations, the higher the quality of the interference mitigated signal,however the larger the latency. As illustrated by block 1102, an OFDMsymbol can be received. As illustrated by block 1104, the iterationcounter N can be set to one as the first iteration is occurring. Asillustrated by block 1106, the interference in the received signal canbe estimated using a least squares method to create a polynomialequation as described above with reference to FIG. 8.

As illustrated by block 1110, the estimated interference can besubtracted from the received signal or the received OFDM symbol. Aninterference mitigated signal containing the desired signal can result.The desired signal can be extracted from the noise reduced OFDM symbol,as illustrated by block 1112. As illustrated by decision block 1114, itcan be determined if the number of iterations is equal to number ofdesired iterations or if the error is less than a predetermined amount.If the system has reached the desired number of iterations or the erroris sufficiently low, the data can be recovered from the interferencemitigated signal as illustrated by block 1120.

As illustrated by block 1114, if the system has not iterated the desirednumber of times, or the error is not below a predetermined level theOFDM symbol can be reconstructed by adding the extracted desired signalto the interference estimation, as illustrated by block 1116. Thereconstructed signal can be subtracted from the received signal toprovide an indication regarding the inaccuracy of the estimate asillustrated by block 1118. The result of such a subtraction can yieldthe interference mitigate/desired signal and the interference portion ofthe signal that was not cancelled out by the estimated interferenceequation.

As illustrated by block 1122, the iteration counter can be incremented.As illustrated by block 1106, analyzing the data representing theinterference mitigated signal, the received signal and the estimatedinterference component, the interference that has not been properlyestimated and cancelled can be determined. The system can again estimatethe interference using originally received data, estimated interferencedata and data regarding interference that was notaccurately/appropriately estimated as provided at block 1118. Theprocess can end when the desired iterations or the desired error levelhave been achieved at block 1114.

Traditional systems replicate an interference signal that is obtainedfrom a cross connected copy of the interference signal or by means oftwo or more independent paths so that an actual copy of the interferenceis subtracted from the desired signal. The disclosed methods provide ablind but accurate derivation of a replica of the interference withoutthe use of a cross connects or duplicate path. In this case, a timedomain estimate of the interference is desired since it avoids the crossmodulation problems associated with transforming to the frequencydomain.

The calculated estimate is a desired solution when the interferingsignal levels of concern are greater than the level of the desiredsignal by a predetermined amount. This condition can be checked firstand when the interference energy level is higher than the desired signallevel, the received signal can be sampled and the disclosed methods canprovide an equation that fits the interference function over thesampling period. By sampling the combined desired signal andinterference it is economical to estimate the narrowband waveform thatconstitutes the interference. The estimated interference can then beutilized to generate an anti phase with respect to the incoming signaland combined with a delayed version of the combined signal. Thus, addingthese waveforms can effectively cancel the interference.

To achieve an improved desired signal the accuracy of the interferenceestimation can be improved. In some embodiments, the interferenceestimation or replication can utilize an iterative process or arecursive process where the estimation can become more accurate witheach iteration. The number of iterations can be limited by latencyrequirements, however only a few iterations are required to achieve thedesired accuracy. Such an iterative process is referred to as aturbo-cancellation method herein.

When the received interference is at low levels, the estimation methoddescribed above can be less than perfect. The described iterativeprocess allows interference to be more accurately estimated even whenthe interference is at these relatively low levels. However, even athigh interference levels, the turbo-cancellation method described canprovide a more accurate interference estimate, thus allowing the systemto extract an accurate version of the desired signal. The disclosediterative process allows for a less complex system to generate theinterference estimate.

The turbo-cancellation method can extend the time domain cancellationtechniques described above by continually improving the accuracy of anequation that estimates the incoming interference. Such arrangements canutilize an iterative “turbo technique” to obtain a more accurateestimation and cancellation of the interference using two or more stagesof estimation and cancellation. Generally, the more accurate theestimation the better data recovery or the lower the error rate.

The disclosed time domain cancellation arrangements can provide a veryaccurate replication (estimation) of the interference. Such an accuratesignal can then be subtracted from the received signal (i.e. thecombined interference plus desired signal). In some embodiments, theestimation is more accurate when there is a high level of interferenceor there is a relatively low signal to noise ratio.

It can be appreciated that there is a trade-off between the timerequired for the interference estimation to iterate using the turboapproach and overall performance. Using the iterative turbo approach theinterference can be estimated more accurately and/or the complexity ofthe estimation can be decreased. For example, the iterative turboapproach allows implementation of the time domain cancellation usinglower order polynomials than required for a single stageestimator/canceller and, subject to adequate range being available inthe ADC, allows cancellation of signals at a greater interference tosignal ratio. However, the iteration takes more time than single stepinterference estimation and can increase latency. Thus, there is acost/benefit tradeoff for such an iterative process.

Each process disclosed herein can be implemented with a softwareprogram. The software programs described herein may be operated on anytype of computer, such as personal computer, server, etc. Any programsmay be contained on a variety of signal-bearing media. Illustrativesignal-bearing media include, but are not limited to: (i) informationpermanently stored on non-writable storage media (e.g., read-only memorydevices within a computer such as CD-ROM disks readable by a CD-ROMdrive); (ii) alterable information stored on writable storage media(e.g., floppy disks within a diskette drive or hard-disk drive); and(iii) information conveyed to a computer by a communications medium,such as through a computer or telephone network, including wirelesscommunications. The latter embodiment specifically includes informationdownloaded from the Internet, intranet or other networks. Suchsignal-bearing media, when carrying computer-readable instructions thatdirect the functions of the present disclosure, represent embodiments ofthe present disclosure.

The disclosed embodiments can take the form of an entirely hardwareembodiment, an entirely software embodiment or an embodiment containingboth hardware and software elements. In some embodiments, the methodsdisclosed can be implemented in software, which includes but is notlimited to firmware, resident software, microcode, etc. Furthermore, theembodiments can take the form of a computer program product accessiblefrom a computer-usable or computer-readable medium providing programcode for use by or in connection with a computer or any instructionexecution system. For the purposes of this description, acomputer-usable or computer readable medium can be any apparatus thatcan contain, store, communicate, propagate, or transport the program foruse by or in connection with the instruction execution system,apparatus, or device.

System components can retrieve instructions from an electronic storagemedium. The medium can be an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system (or apparatus ordevice) or a propagation medium. Examples of a computer-readable mediuminclude a semiconductor or solid state memory, magnetic tape, aremovable computer diskette, a random access memory (RAM), a read-onlymemory (ROM), a rigid magnetic disk and an optical disk. Currentexamples of optical disks include compact disk—read only memory(CD-ROM), compact disk-read/write (CD-R/W) and DVD. A data processingsystem suitable for storing and/or executing program code can include atleast one processor, logic, or a state machine coupled directly orindirectly to memory elements through a system bus. The memory elementscan include local memory employed during actual execution of the programcode, bulk storage, and cache memories which provide temporary storageof at least some program code in order to reduce the number of timescode must be retrieved from bulk storage during execution.

Input/output or I/O devices (including but not limited to keyboards,displays, pointing devices, etc.) can be coupled to the system eitherdirectly or through intervening I/O controllers. Network adapters mayalso be coupled to the system to enable the data processing system tobecome coupled to other data processing systems or remote printers orstorage devices through intervening private or public networks. Modems,cable modem and Ethernet cards are just a few of the currently availabletypes of network adapters.

It will be apparent to those skilled in the art having the benefit ofthis disclosure that the disclosure contemplates methods, systems, andmedia that can provide the above mentioned features. It is understoodthat the form of the embodiments shown and described in the detaileddescription and the drawings are to be taken merely as possibly ways tobuild and utilize the disclosed teachings. It is intended that thefollowing claims be interpreted broadly to embrace all the variations ofthe example embodiments disclosed.

What is claimed is:
 1. A method comprising: detecting a first arrivaltime of an occurrence of interference, the interference havingcharacteristics; detecting the characteristics of the interference;detecting a second arrival time of second occurrence of interference,the interference having at least some of the characteristics;determining a time interval between the first arrival time and thesecond arrival time; and activating a control signal that anticipates anarrival time of future occurrences of interference at a time based onthe time interval, the control signal to activate a narrowbandinterference mitigation feature of a receiver.
 2. The method of claim 1,further comprising comparing the detected characteristics tocharacteristics in a library of characteristics to obtain additionaldata related to the interference from the library.
 3. The method ofclaim 1, further comprising down converting a baseband signal includingthe interference to zero, based on a relative carrier frequency of adesired signal and a relative carrier frequency of an interferingsignal, performing matrix multiplication, performing a subtracting fromthe received signal and up converting a resulting signal back to thebaseband frequency.
 4. The method of claim 2, wherein the data is datarelated to mitigating the interference.
 5. The method of claim 3,further comprising transmitting at least one control signal such that atleast one interference mitigation feature can be activated.
 6. Themethod of claim 5, wherein the at least one interference featurecommences interference mitigation prior to, or concurrently with theanticipated arrival time.
 7. The method of claim 1, further comprisingdetecting a time duration of an interference and, based on the detectedtime duration, predicting at least one timing characteristic of futureinterference.
 8. The method of claim 7, further comprising monitoringinterference when there is an anticipated arrival time and ananticipated time duration of interference and determining that aninterference level during the time duration is below a predeterminedlevel and deactivating the control signal that anticipates an arrivaltime of interference.
 9. A method comprising: detecting time basedinterference, the time based interference having frequencycharacteristics and timing characteristics; detecting at least one ofthe timing characteristics or at least one of the frequencycharacteristics; querying a library with at least one of the detectedfrequency or timing characteristics to locate additional characteristicsrelated to the time based interference; and activating a control signalof a receiver at a time based on the timing characteristics if theadditional characteristics are located, the additional characteristicsincluding a control profile.
 10. The method of claim 9, wherein thecontrol signal is a control signal to activate one of an interferencemitigation feature, a preset gain of an amplifier, a time samplingfeature, a time based interference anticipation feature, a time domaininterference detector, a filter, an interference estimator or aninterference cancellation feature.
 11. The method of claim 9, whereinactivating comprises activating an interference mitigation feature priorto, or concurrently with an anticipated arrival time a next interferencepulse.
 12. The method of claim 9, further comprising accepting aplurality of detector inputs to acquire the at least one timingcharacteristics or the at least one frequency characteristic, andcreating a profile of the detected time based interference.
 13. Themethod of claim 12, further comprising utilizing the created profile toquery the library.
 14. The method of claim 9, further comprising storingthe at least detected timing characteristics or the at least onefrequency characteristics in the library in response to the at least onedetected timing characteristics or the at least one frequencycharacteristics being absent in the library.
 15. The method of claim 14,further comprising creating an interference mitigation control profileto mitigate the detected time based interference, the control profilehaving more than one control signal and associating the control profilewith the signal profile for the at least detected timing characteristicsor the at least one frequency characteristics.
 16. The method of claim11, further comprising monitoring interference when there is ananticipated arrival time and an anticipated time duration ofinterference and determining that an interference level during theanticipated time duration is below a predetermined level anddeactivating the control signal that anticipates the arrival time ofinterference.
 17. A system comprising; a timing detector to detect aperiodically interfering signal; to detect a first arrival time of anoccurrence of interference, the interference having characteristics; andto detect a second arrival time of second occurrence of interference,the interference having at least some of the characteristics of theperiodically interfering signal; an interference profiler coupled to thetiming detector to create a profile of the interfering signal, whereincreation of the profile comprises determination of a time intervalbetween the first arrival time and the second arrival time; and aninterference mitigation module to provide interference mitigation to adata recovery system in response to the created profile of theinterfering signal at a time based on the profile to anticipate anarrival time of future occurences of the interfering signal, wherein theinterference mitigation comprises activation of a control signal thatanticipates an arrival time of future occurrences of interference at atime based on the time interval, the control signal to activate anarrowband interference mitigation feature of the system.
 18. The systemof claim 17, wherein the profile of the interfering signal comprises atleast one frequency of the signal, a duration of the interference, and acycle time of the interference.
 19. The system of claim 17, furthercomprising a library module coupled to the interference profiler tocompare the profile of the interfering signal to profiles in thelibrary.
 20. The system of claim 17, wherein the interference mitigationcontrol module to select an interference mitigation module based on theprofile of the interference.
 21. A receiver comprising; an antenna; atiming detector to be coupled to the antenna to detect a periodicallyinterfering signal to be received by the antenna; to detect a firstarrival time of an occurrence of interference, the interference havingcharacteristics; and to detect a second arrival time of secondoccurrence of interference, the interference having at least some of thecharacteristics of the periodically interfering signal; an interferenceprofiler coupled to the timing detector to create a profile of theinterfering signal, wherein creation of the profile comprisesdetermination of a time interval between the first arrival time and thesecond arrival time; and an interference mitigation module coupled tothe interference profiler to provide interference mitigation in responseto the created profile of the interfering signal at a time based on theprofile to anticipate future occurrences of the interfering signal,wherein the interference mitigation comprises activation of a controlsignal that anticipates an arrival time of future occurrences ofinterference at a time based on the time interval, the control signal toactivate a narrowband interference mitigation feature of the receiver.22. The receiver of claim 21, wherein the profile of the interferingsignal comprises at least one frequency of the signal, a duration of theinterference, and a cycle time of the interference.
 23. The receiver ofclaim 21, further comprising a library module coupled to theinterference profiler to compare the profile of the interfering signalto profiles in the library.
 24. The receiver of claim 21, furthercomprising a data recovery module coupled to the interference mitigationmodule.